Organisms are often adapted to their local environment, but the role of early life stages in adaptive differentiation among populations remains poorly known. The aim of my thesis was to investigate the contribution of early life stages to the magnitude and genetic basis of local adaptation, and to identify the underlying adaptive traits. For this, I used two natural populations of the annual plant Arabidopsis thaliana from Italy and Sweden, and a Recombinant Inbred Line (RIL) population derived from a cross between these populations. By combining greenhouse and field experiments, Quantitative Trait Loci (QTL) mapping, and path analysis, I examined (1) the genetic basis of seed dormancy, (2) the contribution of differential seedling establishment to local adaptation, (3) among-year variation in selection during seedling establishment, (4) direct and indirect effects of seed dormancy and timing of germination on fitness, and (5) the adaptive value of the seed bank. I found that both the level and the genetic basis of seed dormancy were affected by the maternal environment. One major-effect QTL was identified in all maternal environments, which overlaps with the dormancy gene DELAY OF GERMINATION 1 (DOG1). Selection through seedling establishment success contributed strongly to local adaptation and genetic tradeoffs, and varied among years. Variation in seedling establishment and overall fitness among RILs could be explained by genetically based differences in seed dormancy and timing of germination. Seed dormancy affected fitness throughout the life cycle, by affecting the proportion of germinated seeds, and indirectly via effects on timing of germination, plant size and flowering time. My results suggest that a considerable portion of A. thaliana seeds enter the seed bank. I found genetic differences in dormancy cycling behaviour between the two populations, which could contribute to local adaptation. The value of a seed bank should be higher at the Swedish study site than at the Italian study site due to lower rate of seed mortality in the soil. Overall, the results of this thesis demonstrate that early life stages contribute strongly to both the magnitude and the genetics of local adaptation.

A variabilidade espacial e temporal do suprimento larval pode influenciar fortemente as taxas de recrutamento em populações de invertebrados marinhos do entre marés, e, assim, determinar os padrões de abundância e distribuição de adultos. No entanto, o comportamento de larvas antes do assentamento, e a sua condição fisiológica, podem também desempenhar um papel importante. Há vários fatores que influenciam a qualidade fisiológica de uma larva, sendo um deles o efeito materno, ou seja, a forma como os recursos são manipulados pelas mães para produzir sua prole, especialmente como afeta a fecundidade. Outro fator importante é o estado trófico do ambiente onde estágios iniciais se desenvolvem em estágios finais pré-competentes. No entanto, pouco se sabe sobre a relação entre esses dois processos e se a variabilidade natural das condições da costa realmente provoca uma pior qualidade no desempenho juvenil e nas taxas de recrutamento. Neste estudo nós analisamos se os processos que afetam a qualidade embrionária e larval são independentes ou interativas, e também se as condições ambientais ao longo de uma costa subtropical pode mediar tendências de qualidade de larvas à mesoescala e também determinar padrões de distribuição de invertebrados sésseis do entre marés. Usamos a craca Chthamalus bisinuatus como modelo biológico, e experimentos de laboratório e de campo foram realizados para explorar a relação de diversas variáveis ambientais nos padrões de distribuição destes cirripédios. Testamos também se as oscilações naturais na disponibilidade de alimento determinam padrões espaciais e temporais da qualidade da larva produzida e os efeitos da disponibilidade de alimento para as mães e para os seus descendentes na qualidade do estágio larval final deste organismo. Os resultados obtidos nessa tese apontam para a importância da disponibilidade de alimento na coluna d\'água em determinar padrões de abundância e tamanho dos organismos adultos, bem como a relação com o grau de exposição à ação de ondas na manutenção de populações adultas. Concluímos também que mudanças sazonais na produtividade primária tem um efeito na fecundidade e qualidade da larva produzida ao longo do ano por esses cirripédios. Finalmente pudemos demonstrar que pequenas alterações na quantidade de alimento fornecida à mães e larvas de Chthamalus são suficiente para provocar plasticidade de alguns tratos larvais importantes para os processos e sucesso do recrutamento destes organismos. / Spatial and temporal variability of larval supply can strongly influence the recruitment rates in populations of marine intertidal invertebrates, and thus determine the abundance and distribution patterns of adults. However, the behavior of larvae prior to settlement, and its physiological condition, may also play an important role. There are several factors that influence the physiological quality of a larva, one of them being maternal effects, that is, the way resources are allocated by mothers to produce their offspring, especially the way it affects fecundity. Another important factor is the trophic state of the environment where early stages develop into competent pre-final stages. However, little is known about the relationship between these two processes and if the natural variability of coastal conditions actually causes poorer quality in young performance and recruitment rates. In this study we analyzed the processes affecting embryonic and larval quality and if they are independent or interactive, and also if the environmental conditions along a subtropical coast can mediate trends in quality larvae to mesoscale and also determine sessile intertidal invertebrates distribution patterns. We used the barnacle Chthamalus bisinuatus as a biological model, and laboratory and field experiments were conducted to explore the relationship of various environmental variables in the patterns of distribution of these barnacles. We tested also if natural fluctuations in food availability determine spatial and temporal patterns of larvae quality produced and the effects of food availability for mothers and their descendants in the quality of the final larval stage of this organisms. The results obtained in this thesis point to the importance of the food availability in the water column in determining patterns of abundance and size of adult organisms, and the relationship with the degree of exposure to wave action in the maintenance of adult populations. We also conclude that seasonal changes in primary productivity has an effect on fecundity and quality of the larvae produced throughout the year by those barnacles. Finally we were able to demonstrate that small changes in the amount of food provided to mothers and larvae Chthamalus are enough to cause plasticity of some important larval traits which impacts the processes and success of recruitment in these organisms.

Maternal effects are the non-genetic contributions of mothers (or fathers) towards the phenotype of their offspring. Maternal effects are now well recognised as a facilitator for evolutionary change in offspring phenotypes and life history strategies which can have effects on population dynamics, population divergence and even speciation. Furthermore, maternal effects have been shown to have a heritable genetic basis and that they are genetically variable, which suggests that they contribute to maintaining phenotypic variation. Maternal effects may impede or accelerate responses to selection which has implications for adaptive evolution and making predictions about their evolutionary potential. The importance of their contribution to phenotypic variation and life history evolution has made maternal effects an important consideration in fields such as conservation and population biology, evolutionary ecology and evolutionary genetics. The aim of this thesis is to investigate if maternal effects can influence offspring life history traits and fitness parameters through maternal resources via the egg. Main questions that are asked include: can maternal effects help facilitate transition to a novel host-diet (Chapter 2); does maternal diet influence egg composition and, if so, does this have an effect on offspring life-history parameters (Chapter 3); is there a genetic basis to egg composition and is there potential for egg composition to evolve (Chapter 4); and are defensive compounds from the diet transferred into the eggs, if so, are these uni- or biparentally transferred and does this offer protection against predation (Chapter 5)? To address these questions we used a specialist insect herbivore, the large milkweed bug Oncopeltus fasciatus (Hemiptera: Lygaeidae). In the wild, O. fasciatus feed on plants from the genus Asclepias (Apocynacea). However, O. fasciatus can be reared successfully in laboratories on sunflower seeds Helianthus annus. For our experiments we used two populations of O. fasciatus, one population has been maintained on dry seeds of A. syriaca while the other population has been reared and maintained on sunflower seeds. The results of Chapter 2 were suggestive of a maternal host-diet effect on egg mass and hatching success, but we did not find evidence that maternal host-diet was significant in influencing a transition to a novel host. In Chapter 3 we found that there was variation in the free amino acid profiles of the eggs between our treatments suggesting that amino acid profiles may be influenced by maternal diet. The results of our multivariate selection analysis to examine linear and nonlinear (quadratic) relationships between maternal diet and the free amino acid profiles of the eggs suggest that there may be population-specific responses which can influence specific amino acid profiles in relation to hatchling mass. In Chapter 4 we used only the milkweed-adapted population to determine if there was a genetic basis to amino acid profiles in the eggs. We constructed a genetic variance-covariance (G) matrix to determine the strength and direction of the relationships between amino acids and to assess the potential for amino acid profiles to evolve. While we found genetic variation for amino acids, and that there was evidence for positive moderate to strong genetic correlations between many of them, we also found evidence for constraints for the potential for amino acid profiles to evolve as evidenced by the calculation of gmax (which represents the linear combination of components that has the highest genetic variance and which is the most accessible to evolution). In Chapter 5 we found maternal, but not paternal, transmission of cardenolides into the eggs. However, this did not confer protection of all eggs against predation from larvae of the green lacewing Chrysoperla carnea. Overall, results suggest that for our populations of O. fasciatus, maternal effects are significant in influencing early life history traits such as egg mass and hatchling mass. However, we did not find any significant effects on other offspring life history or fitness parameters that we measured. This may be surprising as positive, and negative, effects of non-genetic contributions of females (and males) to their offspring has been widely reported in many taxa. The patterns and implications of maternal resource allocation and their effects on offspring life history evolution are explored and discussed, as are the limitations of our experimental designs. I hope that this research can be used to stimulate further investigations into maternal effects and the relationships between host-plant, maternal allocation strategies and life history evolution.

A trait must genetically correlate with fitness in order to evolve, however, theory suggests that strong directional selection should erode additive genetic variance (Va) in fitness and limit future evolutionary potential. Sexual antagonism and temporal fluctuations in selection are mechanisms that could maintain Va in fitness. Maternal genetic effects could be an additional source of adaptive genetic variation. I used ‘animal models’ to examine a long-term population of red squirrels to determine 1) if either sexual antagonism or temporal fluctuations in selection were maintaining direct Va in fitness or 2) if maternal genetic effects were a source of indirect Va in fitness. While there were environmental trade-offs on juvenile survival, neither sexual antagonism nor temporal fluctuations in selection maintained Va in fitness. Maternal genetic effects on fitness were significant and provide the Va in fitness needed for rapid microevolution. This is the first instance of maternal genetic effects demonstrated as the only genetic variance available for microevolution. / Northern Scientific Training Program, the Arctic Institute of North America, American Society of Mammologists, Queen Elizabeth II Graduate Scholarship in Science and Technology, NSERC Discovery (to Andrew McAdam), NSF (to Andrew McAdam)

A variabilidade espacial e temporal do suprimento larval pode influenciar fortemente as taxas de recrutamento em populações de invertebrados marinhos do entre marés, e, assim, determinar os padrões de abundância e distribuição de adultos. No entanto, o comportamento de larvas antes do assentamento, e a sua condição fisiológica, podem também desempenhar um papel importante. Há vários fatores que influenciam a qualidade fisiológica de uma larva, sendo um deles o efeito materno, ou seja, a forma como os recursos são manipulados pelas mães para produzir sua prole, especialmente como afeta a fecundidade. Outro fator importante é o estado trófico do ambiente onde estágios iniciais se desenvolvem em estágios finais pré-competentes. No entanto, pouco se sabe sobre a relação entre esses dois processos e se a variabilidade natural das condições da costa realmente provoca uma pior qualidade no desempenho juvenil e nas taxas de recrutamento. Neste estudo nós analisamos se os processos que afetam a qualidade embrionária e larval são independentes ou interativas, e também se as condições ambientais ao longo de uma costa subtropical pode mediar tendências de qualidade de larvas à mesoescala e também determinar padrões de distribuição de invertebrados sésseis do entre marés. Usamos a craca Chthamalus bisinuatus como modelo biológico, e experimentos de laboratório e de campo foram realizados para explorar a relação de diversas variáveis ambientais nos padrões de distribuição destes cirripédios. Testamos também se as oscilações naturais na disponibilidade de alimento determinam padrões espaciais e temporais da qualidade da larva produzida e os efeitos da disponibilidade de alimento para as mães e para os seus descendentes na qualidade do estágio larval final deste organismo. Os resultados obtidos nessa tese apontam para a importância da disponibilidade de alimento na coluna d\'água em determinar padrões de abundância e tamanho dos organismos adultos, bem como a relação com o grau de exposição à ação de ondas na manutenção de populações adultas. Concluímos também que mudanças sazonais na produtividade primária tem um efeito na fecundidade e qualidade da larva produzida ao longo do ano por esses cirripédios. Finalmente pudemos demonstrar que pequenas alterações na quantidade de alimento fornecida à mães e larvas de Chthamalus são suficiente para provocar plasticidade de alguns tratos larvais importantes para os processos e sucesso do recrutamento destes organismos. / Spatial and temporal variability of larval supply can strongly influence the recruitment rates in populations of marine intertidal invertebrates, and thus determine the abundance and distribution patterns of adults. However, the behavior of larvae prior to settlement, and its physiological condition, may also play an important role. There are several factors that influence the physiological quality of a larva, one of them being maternal effects, that is, the way resources are allocated by mothers to produce their offspring, especially the way it affects fecundity. Another important factor is the trophic state of the environment where early stages develop into competent pre-final stages. However, little is known about the relationship between these two processes and if the natural variability of coastal conditions actually causes poorer quality in young performance and recruitment rates. In this study we analyzed the processes affecting embryonic and larval quality and if they are independent or interactive, and also if the environmental conditions along a subtropical coast can mediate trends in quality larvae to mesoscale and also determine sessile intertidal invertebrates distribution patterns. We used the barnacle Chthamalus bisinuatus as a biological model, and laboratory and field experiments were conducted to explore the relationship of various environmental variables in the patterns of distribution of these barnacles. We tested also if natural fluctuations in food availability determine spatial and temporal patterns of larvae quality produced and the effects of food availability for mothers and their descendants in the quality of the final larval stage of this organisms. The results obtained in this thesis point to the importance of the food availability in the water column in determining patterns of abundance and size of adult organisms, and the relationship with the degree of exposure to wave action in the maintenance of adult populations. We also conclude that seasonal changes in primary productivity has an effect on fecundity and quality of the larvae produced throughout the year by those barnacles. Finally we were able to demonstrate that small changes in the amount of food provided to mothers and larvae Chthamalus are enough to cause plasticity of some important larval traits which impacts the processes and success of recruitment in these organisms.

No description available.

No description available.

Over the past twenty years there has been an exponential increase in the investigation of maternal effects. Understanding the adaptive function of maternal allocation strategies is integral to interpreting the evolutionary outcomes of sexual selection. Thus, model animal systems that facilitate experimental manipulation and controlled investigation of the physiological and behavioural mechanisms underlying maternal effects are important to evolutionary biologists. The zebra finch (Taeniopygia guttata) has been used as a model to investigate avian life-history, signalling behaviour, neurophysiology, mate choice, and more recently, maternal effects. However, a potentially influential and rarely addressed problem with this species is the process of domestication. Within this thesis we aimed to both test current predominant maternal allocation hypotheses, but for the first time in both domesticated and wild zebra finches. Chapter 2 develops on earlier work using domesticated zebra finches that has demonstrated differential allocation of maternally derived yolk androgens and antioxidants in eggs dependent on paternal attractiveness. This chapter specifically tests the ratio of these two yolk resources within individual eggs and shows that the balance of androgens to antioxidants varies by offspring sex and paternal attractiveness. Specifically, we found that mothers allocated a smaller androgen to antioxidant ratio to daughters when paired to green ringed (unattractive) males compared to red ringed (attractive) males. This pattern was reversed for sons, where mothers allocated a larger ratio of androgen to antioxidant when paired to red ringed (attractive) compared to green ringed (unattractive) males. We also show that brood sex ratio depended on both female condition and male attractiveness. It is concluded that investigating female allocation of individual resources within egg yolks may lead to incorrect assumptions on offspring fitness consequences, and that individual female state is an important consideration when predicting a resource allocation strategy. Throughout this thesis colour bands are used as a method to manipulate male attractiveness. In chapter 3 the influence of these bands was further tested to elucidate whether they affect male behaviour or quality. Wild birds were used for this chapter as preferences for bands based on colour have only once been demonstrated in wild birds and it was felt this should also be replicated. We confirmed a female preference for males based on colour bands worn in mate choice trials, with red bands preferred over green. Interestingly, we also found that colour of bands worn by males for an extended period in the single sex aviary influenced both their song rate and condition. Males that had worn red bands sang more in mate choice trials than both green banded or un-banded males. In addition red banded males were found to be in significantly better physical condition. These data suggest that earlier experiments in which it has been assumed that colour bands do not manipulate any form of intrinsic male quality should be re-evaluated. The final two data chapters, 4 and 5, return to investigating maternal allocation in response to male attractiveness, but for the first time in wild birds. Chapter 4 presents an experiment that was conducted on a wild, nest box breeding population of birds. Maternal resources allocation was investigated in both an experimental manipulation of male attractiveness, and also by correlating resource allocation with paternal phenotypic traits. A limited sample size meant few conclusions could be drawn from the experimental study, but significant positive correlations were found between both egg size and yolk testosterone (T) concentration and male phenotypic traits. This suggested that wild zebra finches may follow a positive investment strategy but requires further investigation. In chapter 5 experiments were repeated on wild birds that had been brought into captivity, to allow both an improved sample size and further control of influential environmental features. Again, female allocation strategies are tested using colour bands to manipulate male attractiveness, to allow direct comparisons with work on domesticated zebra finches. We found that females laid significantly heavier eggs for attractive compared to unattractive males, supporting the positive investment hypothesis. In addition we found an interaction between offspring size and paternal attractiveness treatment, with daughters of red banded (attractive) males being smaller than sons. This experiment is the first to demonstrate the influence of colour bands on maternal allocation in wild zebra finches and also provides further support for the positive investment hypothesis in this species. The final chapter discusses how overall patterns of female allocation were shown to be similar among wild and domesticated populations. It is concluded that demonstrated variations between populations and/or contexts reported in these studies cannot be explained by inherent differences between wild and domesticated individuals. Thus, the zebra finch remains a robust and reliable model for testing the evolution of avian maternal allocation strategies.

L'émergence des zoonoses est à relier directement avec les perturbations générées par l'Homme sur son environnement naturel à plus ou moins grande échelle. Sur l'ensemble des zoonoses émergentes chez l'Homme, la majorité provient d'animaux sauvages. L'étude du rôle de la faune sauvage dans la circulation des agents pathogènes est donc cruciale en particulier quand les interfaces faune sauvage/Homme sont fortes. L'objectif de cette thèse a été de comprendre par des approches éco-épidémiologiques à large échelle, la circulation d'agents pathogènes dans les populations d'un oiseau sauvage en contact étroit avec l'Homme, le goéland leucophée (Larus michahellis). Le premier chapitre présente les différentes méthodes utilisées dans la surveillance d'agents pathogènes ainsi que leurs limites lorsqu'elles sont menées en populations naturelles. Ce chapitre met en évidence au travers d'une étude portant sur les virus influenza aviaires, que la quantification des anticorps maternels dans les œufs est un outil efficace. Le second chapitre consiste à élargir l'échelle spatiale de l'étude afin de mettre en évidence plus finement les facteurs éco-épidémiologiques influençant la transmission des virus influenza aviaires dans et entre les populations de goéland leucophée de l'ouest méditerranéen. Enfin, le dernier chapitre repose sur la comparaison des patrons d'expositions obtenus pour des agents pathogènes au mode de transmission vectoriel : les flavivirus. Cette thèse permet de mettre en évidence les patrons d'exposition de certains agents pathogènes (virus influenza aviaire et flavivirus) et d'appréhender les facteurs éco-épidémiologiques potentiellement impliqués dans leurs circulations. Les résultats permettent d'envisager de futurs axes de recherches, nécessaires pour évaluer plus précisément la dispersion de ces virus en Méditerranée. / The emergence of zoonotic diseases is directly linked to the noise generated by humans on the natural environment to a greater or lesser extent. Of all the emerging zoonoses in humans, the majority comes from wild animals. The study of the role of wildlife in the circulation of pathogens is crucial, especially when wildlife/human interfaces are prominent. The aim of this thesis is to understand, using large scale eco-epidemiological approaches, the circulation of pathogens in a close to human population of wild bird, the yellow-legged gull (Larus michahellis). The first chapter presents the different methods used in the monitoring of pathogens and their limitations when they are conducted in natural populations. This chapter further highlights, through a study of avian influenza viruses, that the quantification of maternal antibodies in eggs is an effective tool. The second chapter expands the spatial scale of the study to highlight the finer eco-epidemiological factors influencing the transmission of avian influenza viruses within and between populations of Western Mediterranean yellow-legged gull. Finally, the last chapter is based on the comparison of exposition patterns obtained for vectorial transmission mode pathogens: flaviviruses. This thesis highlights patterns of exposure for certain pathogens (avian influenza virus and flaviviruses) and enables the understanding of the eco-epidemiological factors potentially involved in their circulations. The results allow to consider future areas of research needed to more accurately assess the dispersion of these viruses over the Mediterranean.

Le transfert trans-générationnel d’immunité (TTGI) est défini comme étant une élévation de l’immunocompétence de la descendance suite à la rencontre des femelles avec un organisme pathogène. Le TTGI est un phénomène bien connu chez les vertébrés, chez lesquels il se réalise par le transfert d’anticorps de la mère au jeune. Il n’a été décrit que récemment chez les invertébrés, chez lesquels le support de sa transmission est encore inconnu. Le TTGI apporte un bénéfice aux descendants lorsqu’ils rencontrent l’infection vécue par la mère, dans quel cas l’élévation de leur immunocompétence a un effet protecteur. Cependant, au-delà de ce bénéfice, plusieurs indices suggèrent que le TTGI est un phénomène coûteux pour les organismes. L’évolution du TTGI ne sera permise chez une espèce que lorsque les bénéfices qu’il représente en termes de protection des descendants surpasseront les coûts qu’il représente pour eux en termes de fitness. Ainsi, l’étude de ses coûts et de ses bénéfices nous renseigne sur les pressions de sélection qui ont conduit à son évolution chez les invertébrés. Au cours de cette thèse, j’ai associé l’expression du TTGI chez un insecte avec un certain nombre de coûts, tant pour les femelles qui le réalisent que pour les descendants qui l’expriment. Pour ce faire, j’ai utilisé comme organisme modèle le ver de farine, Tenebrio molitor. Dans le premier chapitre, nous avons stimulé le système immunitaire des femelles adultes de T. molitor avec un immunogène non pathogène, et étudié divers aspects de la transmission d’activité antibactérienne aux œufs qui en résultait. Cela nous a permis de voir que la transmission d’activité antibactérienne interne aux œufs commençait deux jours après la stimulation du système immunitaire des femelles et cessait après dix jours. Enfin, nous avons pu mettre en évidence un coût pour les femelles à la protection de leurs œufs, en termes de fécondité. Dans le second chapitre, nous stimulé le système immunitaire avec trois microorganismes différents tués par la chaleur, et exposé leurs jeunes larves à des microorganismes vivants. Nous n’avons pas réussi à mettre en évidence d’effet protecteur du TTGI sur les jeunes larves de T. molitor. Il s’avère cependant que l’exposition des jeunes larves à un champignon entomopathogène réduit le délai avant leur seconde mue larvaire. Dans le troisième chapitre, nous avons stimulé soit le système immunitaire des femelles, soit celui des mâles de T. molitor avec un immunogène non pathogène, et observé différents paramètres de l’immunité de leurs descendants adultes. Cela nous a permis de mettre en évidence que le TTGI d’origine maternelle et paternelle n’affecte pas les mêmes effecteurs immunitaires chez les descendants, et que le TTGI d’origine maternelle comportait un coût pour eux en termes de temps de développement. Ces coûts au TTGI suggèrent qu’il n’est pas seulement une conséquence de la stimulation du système immunitaire des femelles de la génération parentale, mais qu’il est bien un mécanisme qui a été sélectionné du fait des bénéfices qu’il représente pour les organismes dans certaines conditions écologiques / Trans-generational immune priming (TGIP) is defined as the plastic enhancement of offspring's immunocompetence following an immune challenge of the females of the parental generation. In vertebrates, this phenomenon is well described, and is achieved by the maternal transfer of antibodies. In invertebrates however, it has only recently been described. Since invertebrates do not possess antibodies, the mechanism of this transmission remains unknown. If the offspring is exposed to the maternal infection, an elevated immunocompetence can help it cope better with it. Nonetheless, apart from this benefit, several cues indicate that the TGIP bears some fitness costs for individuals. The evolution of TGIP will be favoured when its benefits outweigh its fitness costs. Thus, studying its costs and benefits can lead us to a better understanding of the selection pressures that lead to its evolution in invertebrates. During my thesis, I associated the occurrence of TGIP in an insect, the mealworm beetle Tenebrio molitor, to several fitness costs for the females transmitting it as well as for the offspring receiving it.In the first chapter, we stimulated the adult female's immune system with a non pathogenic immunogene, and studied several aspects of the subsequent transfer of antibacterial activity to the eggs. We saw that the transmission of antibacterial activity inside the eggs started two days after the immune challenge, and stopped at ten. Then, we highlighted a cost for the females on their fecundity to this transmission.In the second chapter, we stimulated the immune system of the females with three different heat-killed microorganisms, and exposed their larval progeny to living microorganisms. We did not see any benefit of the TGIP on the young larvae of T. molitor. However, we saw that the exposure of young larvae to an entomopathogenic fungus decreased the time-lap between the two first larval moults.In the third chapter, we stimulated the immune system of either the adult females or the males of T. molitor, and we observed several immune parameters in their adult offspring. This allowed us to see that maternally and paternally-derived TGIP affected different immune effectors in the adult offspring, and that maternally-derived TGIP bear a cost on the developmental time of the offspring.These fitness costs to the TGIP suggest that it is not just a side-effect of the immune reaction of the females, but rather an investment that has been selected because of the benefits it represents for the offspring in certain ecological conditions